Ionic conductivity is commonly associated with the flow of ions through a liquid solution of salts. In the vast majority of practical uses of ionic conductors, i.e., as electrolytes for dry cell and sealed lead acid batteries, the liquid solution is immobilized in the form of a paste or gelled matrix or is absorbed in a separator to overcome the difficulties associated with handling and packaging a liquid. However, even after immobilization, the system is still subject to possible leakage, has a limited shelf life due to drying out or crystallization of the salts and is suitable for use only within a limited temperature range corresponding to the liquid range of the electrolyte. In addition, the use of a large volume of immobilizing material has hindered the aims of miniaturization and lowers the output capacity.
Improved microelectronic circuit designs have generally decreased the current requirements for electronic devices. This in turn has enhanced the applicability of solid electrolyte power sources which usually can deliver currents only in the microampere range. These solid electrolyte systems have the inherent advantages of being free of electrolyte leakage, corrosion and internal gassing problems due to the absence of a liquid phase. In addition, they also have a much longer shelf life than the conventional liquid electrolyte power sources.
In attempting to avoid the shortcomings of liquid systems, investigators have surveyed a large number of solid compounds seeking to find compounds which are solid at room temperature and have specific conductances approaching those exhibited by the commonly used liquid systems. Solid electrolytes must be essentially electronic insulators so as not to internally short the cell while at the same time they must allow for ionic migration if the cell is to operate properly. There are many solid state electrolytes "disclosed" in the art that can be used for solid state cells but many can only operate efficiently at higher temperatures, have low operating voltages or have internal high resistance.
It is an object of the present invention to provide a method for assembling a solid electrolyte cell, specifically a flat solid electrolyte cell.
It is another object of the present invention to provide a method for assembling a solid electrolyte cell employing a solid electrolyte film containing poly(ethylene oxide) or a poly(ethylene oxide) type polymer in conjunction with ethylene carbonate and propylene carbonate.
It is another object of the present invention to provide a method for assembling a solid electrolyte cell employing an active cathode film containing poly(ethylene oxide) in conjunction with ethylene carbonate and propylene carbonate.
The foregoing and additional objects will become more fully apparent from the following description and drawing.